The present invention relates to a refrigeration suction mechanism for a piston type compressor. The refrigeration suction mechanism according to the present invention comprises a rotary valve which has a refrigerant introducing passage communicating with a passage extending through a rotary shaft to introduce refrigerant into a compression chamber within a cylinder bore.
A piston type compressor has a plurality of pistons each disposed in a cylinder bore in the circumference of a rotary shaft, so as to convert a rotation of the rotary shaft into reciprocating linear motion of the pistons through a cam.
Piston type compressors disclosed in Japanese Laid-Open Patent Publication 5-113174 and Japanese Laid-Open Patent Publication 7-63165 comprise a rotary valve for introducing refrigerant into the cylinder bores. A variable discharge swash plate type compressor disclosed in Japanese Laid-Open Patent Publication 5-113174 comprises a rotary valve which is separately formed from and connected to a rotary shaft. The rotary valve is rotatably contained in a valve chamber so as to allow rotational motion of the rotary shaft.
Japanese Laid-Open Patent Publication 7-63165 discloses a swash plate type compressor using double-headed pistons. The compressor has a suction passage radially extending in a journal portion of a rotary shaft and communicating with a refrigerant passage extending through the rotary shaft. The suction passage communicates with a suction port of one of cylinders that is in suction stroke as the suction passage rotates. In other words, the rotary shaft acts as a rotary valve. The suction port disclosed in the above publications is selectively opened by the rotary valve to introduce refrigerant into the cylinder bore. This improves volume efficiency compared to the compressor with a suction port selectively opened by a suction valve that can be distorted.
However in any of the compressors disclosed in the above publications, refrigerant contained in a cylinder bore which is in suction stroke is inclined to leak from the suction passage along the outer surface of the rotary valve. More specifically, while the compressor disclosed in Japanese Laid-Open Patent Publication 5-113174 preferred to have a least possible gap between the inner surface of the valve chamber and the outer surface of the rotary valve in order to minimize refrigerant leakage, manufacture of such is very difficult. The compressor disclosed in Japanese Laid-Open Patent Publication 7-63165 has a similar problem with respect to a gap between the through hole provided in a cylinder block and the outer surface of the rotary valve. Such leakage of the refrigerant lowered the volume efficiency of the compressor.